Photos of the deceased are displayed following Mass at the Cathedral of the Holy Cross on the first Sunday after the Boston Marathon bombings on April 21, 2013 in Boston, Massachusetts (AFP Photo / Mario Tama) / AFP

The Tsarnaev brothers suspected in the deadly Boston Marathon bombings were carrying homemade bombs and grenades, which they lobbed at police when cornered, the city’s police commissioner said. He added that the suspects had planned further attacks.

"We have reason to believe, based upon the evidence that was
found at that scene - the explosions, the explosive ordinance that
was unexploded and the firepower that they had - that they were
going to attack other individuals," Commissioner Edward Davis
told CBS's Face the Nation on Sunday.

"That's my personal belief at this time," he continued.

He said that more than 250 spent rounds of ammunition were found at
the scene, and that the ground was "littered with unexploded
improvised explosive devices that we had to point out to the
arriving officers".

Another device was found inside a vehicle the brothers had
previously carjacked.

Speaking with Fox News Sunday in an earlier interview, Davis stated
the suspects “had plans to use those explosives, possibly on
soft targets."

The elder brother, 26-year old Tamerlan Tsarnaev, reportedly got
within three meters of police officers involved in the shootout
before he ran out of ammunition and was tackled. He later died from
wounds sustained in the shootout on Thursday.

His injured younger brother, 19-year-old Dzhokhar Tsarnaev, fled
the scene, forcing officers to conduct a house to house search in
Watertown. He was arrested late on Friday when he was found
seriously injured in the backyard of a private residence.

A transport officer was left seriously wounded in the gun battle
which fatally injured Tamerlan, while the brothers are also
suspected of killing an MIT police officer on the same day.

Davis said tracing back all of the weapons used by the brothers
would constitute a “significant part of the
investigation.”

In a previous interview, Davis reiterated his confidence that the
two individuals responsible for the bombing “are either dead or
arrested at this point,” as authorities believe the brothers
had no accomplices in the attacks.

He further said Dzhokhar Tsarnaev, who was in “serious but
stable condition” after suffering gunshot wounds to the leg and
neck while being apprehended, was “in no condition to be
interrogated at this point in time."

He is expected to be questioned without first having been read his
Miranda rights – which grant him the right to an attorney and the
right to remain silent – due to a rare public safety exception.

The High-Value Detainee Interrogation Group - a multi-security
agency unit tasked with interrogating high-value suspects – is
waiting at the Beth Israel Deaconess Medical Center in Boston,
where Dzhokhar is convalescing under heavy guard.

However, Boston Mayor Tom Menino told ABC's This Week said that
due the extent of Dzhokar’s injuries,“we don't know if we'll
ever be able to question the individual." While the surviving
suspect was expected to be charged over the weekend, prosecutors
have not yet said what charges he would face. It has been
speculated that the naturalized American could be charged with
using a weapon of mass destruction to kill people.

The federal public defender's office in Massachusetts has
already agreed to represent Dzhokhar once he is charged.

Meanwhile, Massachusetts Gov. Deval Patrick told NBC on Sunday
that surveillance footage from the Boston Marathon bombing clearly
put Dzhokhar at the scene of the attack.

"It does seem to be pretty clear that this suspect took the
backpack off, put it down, did not react when the first explosion
went off and then moved away from the backpack in time for the
second explosion," Patrick said.

"It's pretty clear about his involvement and pretty chilling,
frankly." Patrick added that he had not viewed all of the
available video evidence, but had been briefed by law enforcement
officials about it.

Investigators have determined the bombs were fashioned from
pressure cookers packed with explosives, nails and ball bearings
which were hidden in black backpacks.

Three people were killed and more than 180 injured when the two
bombs exploded within 13 seconds of each other near the finish line
of the Boston Marathon on Monday.